Why do I get a message that some one I'm sending in a group mail is "not a Member"?

I have made up a rather large GROUP in my address book. I enter info in the persons name, Screen Name, and enter the complete email address in the appropriate boxes. I check the radio button next to screen name. When I send the message I get the message that the person I am sending to username@example.com is not a member. How do I fix this. When I see help articles about some thin like this I see very explicit simple steps, but the pictorials do not match my screen. They refer to distribution lists. My AOL desktop version is 9.8.2 I think.